1. Field of the Invention
The present invention relates generally to an optical cross-connect device, and more particularly to an optical cross-connect device suitable for construction of a large-scale optical network supporting an increase in number of wavelengths in WDM (wavelength division multiplexing) and also to a system having the device.
2. Description of the Related Art
With high-speed and large-capacity information transmission, it is required to realize a broadband and large-capacity network and transmission system. As one of means for realizing such a network and transmission system, the construction of a WDM (wavelength division multiplexing) based optical network is desired. An optical cross-connect device (optical XC) is known as a core device used in constructing such an optical network.
Referring to FIG. 1, there is shown an example of the configuration of an optical cross-connect device and an optical network. Reference numeral 2 denotes an optical cross-connect device to which a plurality of input optical transmission lines 4 and output optical transmission lines 6 are connected. The optical cross-connect device 2 is a device for routing wavelength division multiplexed optical signals having wavelengths xcex1 to xcexn supplied from each input optical transmission line 4 to a desired one of the output optical transmission lines 6 by the wavelength. The optical cross-connect device 2 is connected through inter-office links to other optical cross-connect devices, and optical amplifiers 8 for compensating for attenuation of optical signals are usually inserted in each inter-office link in the case of long-haul transmission. The optical cross-connect device 2 is further connected through intra-office links to another communication device, e.g., an electrical cross-connect device (electrical XC) 10. These devices are controlled by an operation system 12 managing the whole of the network.
With an increase in transmission capacity, the number of wavelengths in WDM is rapidly increasing in an optical network. The increase in number of wavelengths causes substantial enlargement in scale of an optical switch required in the optical cross-connect device, resulting in complexity of the optical cross-connect device. Thus, it is desirable to realize an optical cross-connect device suitable for construction of a large-scale optical network supporting an increase in number of wavelengths.
FIG. 2 is a block diagram showing an example of the configuration of an optical cross-connect device in the prior art. WDM signal light input from each input optical transmission line 4 is demultiplexed by a wavelength demultiplexing section 14 to obtain n optical signals having different wavelengths xcex1 to xcexn, and each optical signal is supplied to a first wavelength converting section 16. The first wavelength converting section 16 converts the input optical signal into an electrical signal, regenerates the electrical signal, and then reconverts the electrical signal into an optical signal having a required wavelength, which is next supplied to an optical switch 18. The optical switch 18 performs routing of the input optical signal to a desired output port. The wavelength of the optical signal thus routed is next converted into a wavelength for an optical transmission line by a second wavelength converting section 20. The n optical signals respectively output from the n second wavelength converting sections 20 are wavelength division multiplexed by a wavelength multiplexing section 22, and resultant WDM signal light is output to an output optical transmission line 6.
FIG. 3 is a block diagram showing an example of the configuration of another optical cross-connect device in the prior art. In this example, a time division signal demultiplexing section 24 and a time division signal multiplexing section 26 are used in place of each first wavelength converting section 16 and each second wavelength converting section 20 shown in FIG. 2, respectively, and a space switch 28 is used in place of the optical switch 18 shown in FIG. 2. In the case that the transmission speed of one wavelength is high (e.g., 40 Gb/s), this wavelength is split into lower-order (e.g., 10 Gb/s) electrical signals by the time division signal demultiplexing section 24, and these lower-order electrical signals are supplied to the space switch 28. The signals output from the space switch 28 are time division multiplexed by each time division signal multiplexing section 26, and converted into an optical signal. The n optical signals respectively output from the n time division signal multiplexing sections 26 are wavelength division multiplexed by a wavelength multiplexing section 22.
In the prior art shown in FIG. 2 or 3, a large-scale optical switch or space switch (the space switch being configured by an electrical switch or an optical switch) becomes necessary in the case of configuring a large-capacity optical cross-connect device. However, it is difficult to reduce the size of the device by the existing switching technique. Particularly in the configuration shown in FIG. 2, opto/electric conversion and electro/optic conversion are required in each of the first and second wavelength converting sections 16 and 20. Accordingly, preliminary installation of such converters by the wavelength causes a substantial reduction in efficiency.
It is therefore an object of the present invention to provide an optical cross-connect device suitable for construction of a large-scale optical network supporting an increase in number of wavelengths, and to also provide a system including the device.
The other objects of the present invention will become apparent from the following description.
In accordance with an aspect of the present invention, there is provided an optical cross-connect device. This device comprises k (k is an integer satisfying 1xe2x89xa6k) first wavelength demultiplexing sections each for receiving WDM signal light obtained by wavelength division multiplexing n (n is an integer satisfying 1xe2x89xa6n) optical signals having different wavelengths to demultiplex said WDM signal light into said n optical signals; k wavelength group generating sections each for receiving said n optical signals output from each first wavelength demultiplexing section to generate i (i is an integer satisfying n=im where m is an integer satisfying 1xe2x89xa6m) wavelength groups each having m wavelengths; ik first wavelength multiplexing sections each for receiving each wavelength group output from each wavelength group generating section to multiplex the wavelengths of each wavelength group and then output a resultant WDM wavelength group; a routing section having at least ik input ports and ik output ports for routing said WDM wavelength groups between said input ports and said output ports; ik second wavelength demultiplexing sections each for receiving said WDM wavelength group output from each output port of said routing section to output a wavelength group having m wavelengths; kn wavelength converting sections each for performing wavelength conversion of each optical signal in said wavelength group output from each second wavelength demultiplexing section so as to correspond to said WDM signal light; and k second wavelength multiplexing sections each for receiving n optical signals output from said wavelength converting sections to wavelength division multiplex said n optical signals and then output resultant WDM signal light.
In accordance with another aspect of the present invention, there is provided a system suitable for construction of a large-scale optical network. This system includes a plurality of optical cross-connect devices connected by optical transmission lines. At least one of the optical cross-connect devices comprises an optical cross-connect device according to the present invention.